Physics [2 Mark Question Answer]

In sheaf pulley system there are two sets of pulleys, each set containing two or more pulleys, these pulleys are mounted on a common axle and are of the same radius. The set of pulleys attached to the high platform is called a block, whereas the set of pulleys attached to the load is called a tackle.

Using a single movable pulley, the load can be lifted by applying an effort equal to half the load, ie., it acts as a force multiplier. On the other hand, single fixed pulley can only be used to change the direction of applied effort.

Single fixed pulley is used widely because:
(a) It is always easier to apply effort in the downward direction rather than in the upward direction. Thus, the pulley helps in changing the direction of effort.
(b) One can use one's own body weight, while applying the effort in the downward direction.

Effort gets multiplied only, if effort arm is longer than load arm. In case of scissors, as effort need not be multiplied, therefore, the effort arm is smaller than load arm.
However, in case of a metal cutter, the resistance due to metal is very large. Thus, effort needs multiplication. It is achieved by making cutting edge (load arm) smaller than the effort arm.

Locate, which amongst the effort, the fulcrum or the load is in the middle. If the fulcrum is in the middle, the lever is of the first order. If the load is in the middle, the lever is of the second order. If the effort is in the middle, the lever is of the third order.

A machine can never be 100% efficient because:
(a) a part of the input is wasted in moving the parts of the machine.
(b) a part of the input is wasted in overcoming friction between the moving parts.

(a) Ideal mechanical advantage is the ratio between the total load (useful load + resistance due to friction and movable parts of machine) moved to the effort applied.
(b) Efficiency is the ratio between the useful output to the actual input of the machine.

(a) Useful load is the actual load lifted by the machine.
(b) Effort is the external force applied on a machine to overcome the load or resistance,
(c) Ideal machine is a machine whose parts are weightless and frictionless, such that the input is equal to the output

(a) Total load is the sum of load lifted by the machine and the load due to friction and movable parts of machine.
(b) Actual mechanical advantage is the ratio between the useful load moved to the effort applied.
(c) Velocity ratio is the ratio of the distance traversed by the effort to the distance traversed by the load in the same time.

(a) Inclined plane, pulley, wedge, screw, wheel and axle, and lever are examples of simple machines.
(b) Inclined plane - A ramp, Pulley Single fixed pulley, Lever-Handle of water pump, Screw A jack screw, Wedge An axe, Wheel and axle - Screw driver

(a) Machine is a device by which we can overcome large resistance or gain speed or change the direction of effort applied, by applying comparatively a small force at a convenient point, and in a desired direction.
(b) (i) A machine can multiply force.
(ii) A machine can increase speed.
(iii) A machine can change the direction of effort applied